Well, you can split the output between two antennas, but it cannot be
haphazard. The connecting cables must be cut a specific length. The
additional connections reduce reliability slightly, though.

The more serious problem, as I understand the installation, is that you will
no longer be ominidirectional. You will have a null straight ahead and
behind you - two critical areas. The antenna would still need to be mounted
vertical, so the new install might be difficult.

Colin